The field of this invention is control valves for providing selective output signals in response to limited input signals to control the operation of an underwater christmas tree or the like.
Presently subsea oil well completions are generally accomplished by mounting on the wellhead a christmas tree having a valve network that is operable from the surface of several different types of systems, such systems being mounted with the christmas tree and extending to a control center at the surface. One such control system in use is an electrohydraulic control system which, although rather sophisticated, is very expensive. Another control system utilizes separate control lines for operating each of the separate valve functions associated with the subsea christmas tree but, the number of control lines needed renders this system very expensive as well as cumbersome.